Add macOS input source switching

[tingkai-c]

Summary

• Add config-only macOS input source switching when RustCast opens
• Restore the previous input source when RustCast closes
• Document the new config fields and feature

Testing

• cargo fmt
• git diff --check
• cargo test (46 passed)
• Manually verified switching from Zhuyin to ABC on RustCast open and restoring Zhuyin on close

[unsecretised]

Hi @tingkai-c

Thank you for contributing to Rustcast. Could you share a few details about this implementation and also if AI was used in the implementation of this feature?

[tingkai-c]

Hi @unsecretised, thanks for taking a look.

Implementation details:

This adds two optional config fields:

• input_source_on_open: macOS input source ID to switch to when RustCast opens, for example com.apple.keylayout.ABC.
• restore_input_source_on_close: restores the previously active input source when RustCast closes.

The switching is implemented in the macOS platform layer using Text Input Source APIs from Carbon:

• TISCopyCurrentKeyboardInputSource
• TISCreateInputSourceList
• TISGetInputSourceProperty
• TISSelectInputSource

RustCast captures the current input source in Message::OpenWindow, switches to the configured source if present, and restores the captured source in Message::HideWindow. If switching fails, it logs the error and keeps RustCast usable.

The configured source must be enabled in macOS Keyboard settings. I used enabled input sources only so disabled IDs fail cleanly instead of selecting unavailable sources.

Testing:

• cargo fmt
• git diff --check
• cargo test passed locally
• Manually verified switching from Zhuyin to ABC on RustCast open, then restoring Zhuyin on close.

AI usage:

Yes, AI assistance was used while developing this PR. I used it as a coding/review aid for repository exploration, implementation drafting, and validation steps. I reviewed the changes manually, tested the behavior locally on macOS.

[unsecretised]

Hi there. Could you elaborate more on what parts were coded with AI? It seems to be that the PR was 100% AI generated and just verified that it works by a human.

As per the contributing guidelines, we don't support 100% AI PRs, as their quality is still not up to the standard I would wish them to be. If I'm wrong about the AI Usage, then please close this PR (I will assume its 100% AI generated if there's no response for the next 1 week and close this PR)

If it isn't 100% AI generated, please share details such as where you used AI, what models, and why you had to use AI.

[unsecretised]

Idk how much AI you used but i decided to review this PR either way.

Its a decent implementation, but I don't see the need for this, and also you're missing the ability to customise this from the settings page.

[unsecretised]

Please use objc2 wherever possible (i know objc2-carbon doesn't expose sufficient APIs but things like the data types should minimally be objc2)

[tingkai-c]

Thanks for reviewing.

The need for this comes from my daily workflow. I used this behavior every day in Raycast: when I’m typing in Zhuyin or another non-Latin input method, I want the launcher to always open in a predictable Latin input source so app search and commands work immediately. Without this, I have to manually switch input sources before using RustCast.

For the Settings page, I agree. I think the UX should be:

• Add a toggle to enable/disable automatic input source switching.
• If enabled, show/enable a dropdown of available macOS input sources.
• Store the selected source in config.
• Keep restoring the previous input source when RustCast closes.

I’ll also update the implementation to use objc2/objc2_core_foundation types where practical, while keeping raw FFI only for the Carbon Text Input Source APIs that are not exposed by objc2-carbon.

On AI usage: AI was used only for repository exploration and implementation drafting. I reviewed the code, tested it locally on macOS, and debugged the input-source behavior. I’m using OpenAI GPT-5.5 high.

If there are coding style rules that I should follow beyond CONTRIBUTING.md, please kindly tell me or point me to where they are documented.

[tingkai-c]

Pushed an update addressing the review feedback:

• Added Settings page controls: a toggle for input source switching and a dropdown of enabled macOS input sources when enabled.
• Updated the input source helper to expose enabled input sources for the dropdown.
• Switched Core Foundation handling toward objc2_core_foundation types (CFArray, CFString, CFRetained) while keeping raw FFI for the Carbon TIS APIs.
• Updated config docs to mention Settings page support.
• Rebasing onto latest master cleared the PR behind state.

Checks:

• cargo fmt
• git diff --check
• cargo test passed locally
• GitHub CI is green

[unsecretised]

looks good to me